PROJECT SUMMARY/ABSTRACT The Data & Methods Core will provide the personnel, expertise, and computational resources needed for effective use of Medicare data and other data to be acquired and analyzed by the investigators in the Program Project. Additionally, it will provide leadership on the data-related issues common to all projects as well as day-to-day direction in the management of complex data sets and analyses. This Core involves four aims. First, the Core will be responsible for all data management and oversight activities including dataset acquisition, preparation, integration, management, and quality control. Second, the Core will offer and coordinate clinical expertise in measurement, specification of key analytic variables, and interpretation across the projects. Almost all aims in the Program Project projects involve some clinical or health data. The explicit clinical linkage will help ensure cross-project learning about fruitful approaches and maximize consistency in approaches across projects. Third, the Core will offer and coordinate expertise on statistical model building and other data analysis methods across all projects. A coordinated approach is particularly important given the common features across projects in the data used and interrelated research questions. Fourth, the Core will apply theory from health economics to supply- and demand-side setting payment innovations. The Data & Methods Core is staffed by senior researchers with extensive experience with the data and methods involved in the Program Project projects. The Medicare program is of enormous importance to the health, welfare and financial status of the elderly and to the federal government and its budget. It is crucial to conduct empirical analysis with broadly representative data, carefully specified measures of clinical quality and resource use, and rigorous statistical methods.